Small molecule mass spectrometric quantitative and qualitative analyses including parent, product and neutral loss scans, as well as highly sensitive characterization of post translational protein modifications, specifically phosphorylation, in a linear quadrupole ion trap mass spectrometer, are both highly needed capabilities for existing NIH-funded investigators at the University of Arizona to advance the science of their research. Funds for a 4000 Q TRAP mass spectrometer from Applied Biosystems are requested to add this hybrid triple quadrupole-linear ion trap to the existing mass spectrometry instrumentation infrastructure of the Proteomics Core of the Southwest Environmental Heath Science Center and the Arizona Cancer within the University of Arizona campus. Currently one 10-yr old triple quadrupole LC-MS/MS system is available through the Proteomics Core for general service use and while it is still functional and useful, it suffers from the sensitivity requirements of many projects. No quadrupole linear ion trap MS system is available on the University of Arizona campus. Quadrupole linear ion traps have been shown to be among the best mass analyzers to date for highly sensitive proteome profiling and for post translational modification mapping due to their increased ion capacity, increased scanning speed, and real-time "smart" scanning functions. Acquisition of this instrument is being supported by 11 NIH-funded investigators from the Departments of Pharmacology and Toxicology, Molecular and Cellular Biology, Chemistry, Pathology, Biochemical and Molecular Biophysics, Cell Biology and Anatomy, and Plant Sciences, all of whom have had MS experience and services performed in the past. The strategic areas of focus for use of this instrument will be (1) small molecule quantitation/characterization and (2) peptide phosphorylation identification/characterization. Manufacturer demonstration data and comparative analyses with existing mass spectrometry resources of realistic samples from these users are presented, and clearly showcase the need and utility for this new state-of-the art mass spectrometer. The support system at the University of Arizona in terms of experienced personnel, organizational and management abilities and usage track record, exists, making acquisition of the 4000 Q TRAP a logical choice to handle the MS-based research and scientific challenges of the future. [unreadable] [unreadable]